The present invention relates to a spring suspension system for vehicles and components of such vehicles which at least to some extent constitute loads, such as vehicle cabs, which are subjected to acceleration in the starting and braking directions. At least one suspension cylinder is provided to which a load may be applied. The fluid chambers of the suspension cylinder are connected to a damping mechanism to carry fluid. The damping mechanism regulates the flow of fluid antagonistic to freedom of movement of the load throttles the flow of fluid connected to the load.
In the case of service vehicles and other utility vehicles in movement the vehicle occupants are to be shielded from jolts, shaking, and vibrations occurring in travel over rough terrain or are caused by the engine or other assemblies. To counteract these effects, spring suspension systems are conventionally used. Distinctions are made, for example, among individual wheel suspensions, axle suspensions, body suspensions, cab suspensions, and/or seat suspensions.
These conventional spring suspension systems employ a spring element that generates restoring force on a change in position of the mass to be cushioned. The force acts in the direction opposite that of the change in position. If systems which additionally generate a force dependent on the direction and magnitude of the relative velocity are used, reference is made to spring shock absorber systems. In conjunction with any spring elements present and the spring mounted mass, such systems form an oscillatory system designed so that passengers in a vehicle can be suitably protected from shocks and impacts.
A spring suspension system is disclosed in DE 28 48 339 C2. This patent discloses an active mechanical-hydraulic control unit to compensate for changes in the position of land vehicles caused by disturbances and also component systems of this unit. The unit includes an acceleration sensor with inertial mass, actuator, center position control unit, and sequence amplifier. A pilot stage is provided to amplify the signal delivered by the acceleration sensor. Since the actuator, sequence amplifier and center position control unit operating independently of the acceleration sensor are integrated into one structural unit, and since a control orifice to control delivery of the pressure medium to return the actuator to its center position is mounted in the actuator, a system with pressure and throughput yield is obtained and simultaneously is of compact design. The system involves a deflecting plate control in which a stream of oil emerges simultaneously from two triggering nozzles and strikes a deflecting plate. When the body of the sensor moves, the deflecting plate is rotated. The distance from the plates to the edge of the nozzle exit is increased on one side, while this distance is decreased on the other side. Conversely, reduction of the distance results in a smaller oil exit stream and an increase in the distance of a larger oil exit stream in the pilot unit. The oil streams behaving in this manner then act on the controlling edge of the movable piston in the suspension cylinder. Independent choking of the oil streams is not achieved by application of this method. In addition, only changes in the position of the suspension cylinder can be additionally adjusted by application of this approach.
DE 43 24 289 A1 discloses an active suspension of a spring-suspended mass, in a suspension of the driver""s cab of a utility vehicle, with actuatable active cylinders between cab and vehicle. This suspension uses vibration energy of another passive or semiactive spring-suspended mass, especially that of the structural suspensions of a utility vehicle, as control energy for actuating the active cylinders of the active suspension. It is expedient in this solution to replace conventional vibration dampers with double-acting differential cylinders mounted in a closed hydraulic circuit of the active spring suspension system. The conventional spring suspension system used for this purpose with actuated active cylinders and valves entails use of a large number of building components in construction. Such building components cause delay determined by the system in application of the damping desired. In addition, even if only one component fails, the operational reliability of the entire system becomes questionable.
An object of the present invention is to provide improved suspensions by providing a user-friendly basic suspension capable of continuing to ensure reliable damping in the event of extreme acceleration and avoidance of dangerous driving conditions of this nature. Another object of the present invention is to provide a spring suspension system making rapid direct control of damping behavior possible with only a small number of structural components.
To control the damping mechanism, a sensor mechanism is provided having a control mass subject to acceleration and acting on at least one throttle mechanism. Increased throttling of the flow of fluid occurs with an increase in acceleration. Within the flow of oil or fluid, a component with a variable cross-sectional aperture varies the cross-sectional area in the opposite direction as a function of the magnitude of acceleration of the vehicle. In the event of high acceleration an appreciably smaller diameter is available at the throttling point. As a result of this smaller diameter, appreciably greater throttling of the oil and fluid flow is achieved. Independent initiation of throttling of the oil flows in the system with short actuation periods is accordingly made possible.
The control mass makes it possible to achieve rapid throttling of the oil flow as a function of the acceleration acting on the vehicle in or opposite the direction of travel so that the damping force desired is rapidly reached as a function of such acceleration. The present invention is based on purely mechanical and hydraulic principles, which increases reliability in operation. In addition, only a small number of structural components are required for the purpose.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.